gh-112069: Do not require lock if the set has never been exposed.

Author: corona10

Diff for: Objects/setobject.c

@@ -2334,6 +2334,12 @@ set_init(PySetObject *self, PyObject *args, PyObject *kwds)
     if (!PyArg_UnpackTuple(args, Py_TYPE(self)->tp_name, 0, 1, &iterable))
         return -1;
 
+    if (self->fill == 0 && Py_REFCNT(self) == 1) {
+        if (iterable == NULL) {
+            return 0;
+        }
+        return set_update_local(self, iterable);
+    }
     Py_BEGIN_CRITICAL_SECTION(self);
     if (self->fill)
         set_clear_internal(self);